Ferroelectric Hafnium Oxide Material Enhanced Reliability

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The main objective of the project is to understand the interplay between a dielectric and a HfO2- or ZrO2-based ferroelectric layer within a capacitor structure. Within this bi-layer structure stack a strong interaction between the ferroelectric dipoles and charges (e.g. electrons, holes, charged oxygen vacancies) occur. Since different thickness ratio of dielectric and ferroelectric layer are present in a wide range of semiconductor devices from ferroelectric capacitor via ferroelectric field effect transistors and ferroelectric tunnel junctions to negative capacitance FETs and infrared sensors, effects might change from one device to another, but basic characteristics remain similar. So far, a detailed understanding of the effects of defects and charges is limited, and further studies are urgently needed to make the introduction of HfO2 based ferroelectric materials in a wide range of applications possible. HfO2- and ZrO2-based ferroelectric layers are doped by atoms with different valence to understand the impact of dopant valence on the ferroelectric capacitor reliability (memory window, leakage, wake-up behavior, retention, fatigue, and endurance). Furthermore, the impact of the thickness ratio of ferroelectric/dielectric layers as well as electrode materials will be studied on the capacitor film stacks to reduce trapping behavior and get better performance. To achieve these results, the electronic and atomic structure of active mediums will be studied by different characterization techniques which will be supplemented and strengthened by experimental luminescence and charge transport experiments with ab initio simulations. Obtained results allow to obtain a detailed microscopic model for the degradation behavior of ferroelectric properties in order to develop practical recommendations for ferroelectric devices. The overall goal of the project is an optimization of this new lead-free ferroelectric material with respect to reliability, performance, environmental compatibility, CMOS compatibility, availability of the basic material.